Instrument for crushing stones in urinary bladder

ABSTRACT

A method and apparatus for non-surgical removal of concretions in the urinary tract. A lithotrite including a central and outer electrode is connected to electric pulser means including spark discharge members for generation of electrical pulses which result in hydraulic shock waves being emitted from the lithotrite. In operation, the lithotrite is placed adjacent the concretion to be crushed which is surrounded by a dielectric fluid. The frequency and/or intensity of the hydraulic shock wave can be varied until the desired crushing of the concretion is achieved.

United States Patent 91 Balev et al.

[451 May 29, 1973 [54] INSTRUMENT FOR CRUSHING STONES IN URINARY BLADDER [76] Inventors: Oleg Gavrilovich Balev, Prospect 40-letia Oktyabrya 100, kv. 174; Jury Grigorievich Ediny, Rovenskaya ulitsa 7, kv. 58; Nikolai Akimovich Korol, Prospect 40-letia Oktyabrya 108/128/17, kv. 3, all of Kiev, U.S.S.R.

[22] Filed: Nov. 23, 1970 [21] Appl. No.: 92,056

Related U.S. Application Data [63] Continuation-impart of Ser. No. 871,849, Oct. 28, 1969, abandoned, which is a continuation-in-part of Ser. No. 444,681, April 1, 1965, abandoned.

52 Us. on. ..12s/32s, 128/24 A 511 int. Cl....A61h 21/00, A6lh 29/00, A6lb 17/00 [58] Field of Search ..128/328, 24 A [56] References Cited UNITED STATES PATENTS 2,227,727 1/1942 Leggiadro ..128/328 X 2,764,683 9/1956 Paust et a1. .,l28/303.17 UX 2,830,578 4/1958 De Grofi' ..128/24 A 3,413,976 12/1968 Roze 128/328 3,557,793 1/1971 Ediny et a1. ..128/328 FOREIGN PATENTS OR APPLICATIONS 1,082,397 9/1967 Great Britain ..128/328 1,284,561 12/1968 Germany 866,946 3/1971 Canada ..l28/328 Primary Examiner-Aldrich F. Medbery Att0rney-Burns, Doane, Swecker & Mathis [57} ABSTRACT 21 Claims, 7 Drawing Figures E :4 1 36 I38 I40 VOLTAGE VAC SUPPRESSION FILTER 52 POW SWITCH PATENTEMMYZSIQB 3.735'764 SHEET 3 OF 3 FIG. 7

U i- I I, V

1 INSTRUMENT FOR CRUSHING STONES IN URINARY BLADDER This application is a continuation-in-part of our application Ser. No. 871,849, filed Oct. 28, 1969, now abandoned which in turn is a continuation-in-part of our application Ser. No. 444,681, filed Apr. 1, 1965,

now abandoned.

This invention relates to instruments intended for crushing concretions in the urinary ducts and more particularly to instruments for crushing stones in the urinary bladder.

Mechanical means such as lithotrites and cystoscopes are known in surgery for crushing stones in the urinary bladder, but they are of little efficiency, inconvenient in operation, and do not ensure complete safety to the patient.

Attempts have been made to solve the problem by instruments employing ultrasonic oscillations imparted to the lithotrite introduced into the urinary bladder to contact the stone to be crushed. Said instruments were allowed to control visually the operation of stone crushing and the possibility of trauma to the patient was eliminated. Moreover, the amount of washing fluid in the urinary bladder was comparatively small.

However, in crushing stones of big size (30 mm. and over), and when the number of stones in the urinary bladder is great, the operation might turn out to be time-and labor-consuming.

It is known that with electrical discharges between two spaced electrodes submerged in liquids such as water and electrolytes, hydraulic shock waves of great intensity can be generated in the region between the electrodes. In the generation of such hydraulic shock waves, a high voltage circuit has been used with one or two atmosphere-filled spark gaps in series circuit arrangement with the spacing between the two electrodes, and studies have shown that the intensity can be controlled by varying not only the voltage applied, but also the number and sizes of the various gap and electrode spacings, and sizes and shapes of electrodes. Spark lengths of between 8 and 200 mm. have been used, and numerous electrodes have been used, some in the shape of a cylindrical bore for producing holes from 40 to 50 mm. diameter in rocks of various hardness. Such equipment used air gaps of about 10 mm., a voltage of 25-30 kv., and a capacitance of 0.2 f. While such equipment was found to disintegrate or chisel crystalline, fibrous and certain schistous rocks, it was not adapted for use by the medical profession. Moreover, prior to our invention, it was not evident that this technology could be safely adapted for use in a urinary bladder because of the voltages required and the likelihood of damage to body tissue.

A primary object of the invention is to work out an instrument ensuring efi'ective crushing of stones of most various types encountered in urology.

Another object of the invention is to work out an instrument for crushing stones in the urinary bladder ensuring safe and reliable operation.

The specific object of the invention is to create an instrument for crushing stones in the urinary bladder by producing a hydraulic impact in the liquid medium which surrounds the stone through the use of electrical discharges.

It is a further object of the present invention to provide a novel method for non-surgical crushing of concretions in the urinary tract through the use of hydraulic shock waves generated by electrical discharges.

The problem has been solved, in accordance with the present invention, by an instrument having an elongated lithotrite introduced into the urinary bladder through the operative cystoscope. The novel lithotrite comprises two coaxial, insulated electrodes, i.e., the central and the outer electrode, which are connected to an electric pulser means by a flexible cable adapted to pass through the urinary tract so that the electrodes can be placed immediately adjacent the concretions to be crushed. The lithotrite is insulated up to the butt end portion of the central electrode, the ends of both electrodes can be located either in the same plane, or in different planes.

The electric pulser means comprises, in important part, pulse-forming dischargers connected with the electrodes of the lithotrite'and to an accumulating device with capacitors which is fed, for instance, from a power transformer. Component sizes and voltages are selected so as to provide sufficient energy to crush the concretions, but insufficient to cause damage to living tissue when operated properly. Power to the electrodes is controlled by a foot operated switch to provide impulses of electrical energy to the electrodes, and this control is rendered operable only when the instrument is properly grounded to avoid electrical shock to the patient. In the illustrated embodiment, the grounding for the remote control is through a grounding system connected with the cystoscope illuminating lamp supply circuit.

Each of the pulse-forming dischargers can be made as a pair of tungsten cylinders having plane-parallel discharge surfaces whose spacings can be adjusted to control the discharge gap between them, and hence the intensity and/or frequency of the hydraulic shock waves.

Windings of said power transformer should preferably be positioned on separate legs with air gaps between them and the windings.

The following is a detailed description to be read in conjunction with the accompanying drawings, in which:

FIG. 1 shows an electric circuit diagram of the instrument for crushing stones in the urinary bladder;

FIG. 2 shows a lithotrite of the instrument of FIG. 1, having the central and the outer electrodes, whose ends are located in one plane (sectional view);

FIG. 3 shows another embodiment of the lithotrite end of FIG. 2 (in section);

FIG. 4 shows the power transformer for the instrument shown in FIG. 1 (in section);

FIG. 5 is an electrical circuit diagram of a preferred embodiment of an electric pulser for use with the lithotrite of FIGS. 2 and 3;

FIG. 6 is a cross-sectional view of a preferred embodiment of the spark discharge members of FIG. 5; and

FIG. 7 shows the cable arrangement for supplying the electrical pulses to the electrodes which are positioned in the urinary bladder adjacent the concretions to be crushed.

The instrument for crushing stones in the urinary bladder has a device for generating electric pulses, a pulse generator 1 (FIG. 1) made as a rectifier in accordance with a doubling circuit employing semiconductor elements 2 and 3. The generator 1 comprises also storage capacitors 4, 5 and two pulseforming dischargers 6, 7 connected to the coaxial electrodes 8, 9. (the central and the outer) of the lithotrite L Electrodes 8 and 9 are separated from each other with insulating material 11 (FIG. 2).

As the electric pulses of the generator 1 produce a spark in the gap between the ends of the inner and the outer electrodes 8, 9 of the lithotrite, hydraulic shock wave is produced in the liquid medium surrounding the stone to be crushed.

The ends of the inner and the outer electrodes 8, 9 may be located either in one plane (FIG. 2) or in different planes (FIG. 3) which allows control of the character of the percussive hydraulic impact. Whatever the embodiment of the lithotrite 10 may be, the insulating material 11 should extend up to the end of the central electrode 9.

The lithotrite shown in FIG. 2 produces directed hydraulic shock waves, while the lithotrite shown in FIG. 3 produces spherical waves of particularly great percussive strength. In the lithotrite shown in FIG. 3, the insulating material 11 should overlap the end of the outer electrode 8. The outer surface of the lithotrites is also coated by an insulating envelope 12. In the lithotrite shown in FIG. 3, the envelope 12 leaves open a portion of electrode 8. To provide for rapid and convenient replacement of the lithotrites 10, the instrument has a high voltage miniature joint 13 (FIG. 1).

Each of the pulse-forming dischargers 6 and 7 is a pair of tungsten cylinders with plane-parallel discharge end surfaces between which adjustable discharge gaps are formed.

The generator 1 is supplied from a power transformer 14 whose windings, e.g., primary 15 (FIG. 4) and secondary 16, are located on separate legs 17 and 18 and have air gaps between them and the legs.

One of the wires supplying power to the relay 33 and lamp 21 of the cystoscope 22 is also shorted through the grounding bus bar 30 by means of the clamp 27. When there is no contact in the grounding circuit, or else if there is no contact between the contact elements 28, 29 of the clamp 27 through the bus bar, the generator 1 is cut out of operation, the lamp 21 of the cystoscope 22 goes down, and the surgeon cannot proceed with the operation.

Suppression filter 35 is provided in the instrument to eliminate radio interference.

All high potential elements of the pulse generator, i.e., capacitors 4, 5, pulse-forming dischargers 6, 7, semiconductor elements 2, 3, and also other elements not shown in the drawings, such as shunting and additional resistors in the rectifier circuit and sockets for connecting the high voltage cable of the lithotrite It), should preferably be installed on insulating plates, which are also not shown in the drawings.

The instrument can be powered from 127 V. and 220 V. 50 cps mains.

The operating procedure is as follows:

Into the urinary bladder is introduced the cystoscope 22 in the end. of which the illuminating lamp 211 is mounted. The bladder is filled with the washing fluid and the lithotrite 10 is passed into the bladder until it comes in contact with the stones to be crushed. As soon as the instrument is switched on, the illuminating lamp 21 of the cystoscope 22 is lighted up, and the pulse generator 1 starts working when the foot pedal 32 is pressed upon, and the mains voltage is supplied to the primary winding of the power transformer 14 through the contacts of relay 33. i

To change the intensity and the repetition frequency of the electric pulses of the generator 1, the primary winding 15 of the transformer 14 has output taps 19 connected to the supply circuit by means of switch 20.

The instrument comprises also a power source for lamp 211 (FIG. i) of the cystoscope 22. This source is the secondary winding of the step-down transformer 23, whose alternating voltage is supplied to lamp 21 of the cystoscope 22 through switch 24 and resistor 25. The switch 24 is intended to set the voltage corresponding to the rated voltage of the lamp 21 which is used. Resistor 25 serves for a smooth adjustment of the voltage. Resistor 26 provides for the current supply to the lamp 211 of the cystoscope 22 in case of break in the circuits of switch 24 and resistor 25. One of the wires supplying power to the cystoscope lamp 2% is connected to a clamp 27 whose contact elements 28, 29 are mutually insulated and have sharpened points for attachment of the clamp 27 to bus bar 30. One of the contact elements 28 of the clamp 27 is stationary and is insulated from the clamp body, while the other contact 29 is movable and connected to the clamp body through a thread joint (not shown in the drawing).

Parallel to the cystoscope 22 lamp 21 supply circuit, a pilot lamp 31 is connected which is used to detect the circuit break.

The pulse generator II is controlled remotely by means of a foot pedal 32 and relay 33 supplied from a rectifier employing diode 34.

Operation of the pulse generator 1 consists in accumulating the charge in capacitors 4, 5 and instantaneous pulsing discharges of this voltage to the circuit of the pulse-forming dischargers 6, 7 and of the lithotrite 10 during the breakdown of the air gaps produced by constant voltage applied from the rectifier.

During the electric breakdown of the discharge cap of the lithotrite, a shock hydraulic wave is formed in the washing liquid which crushes the stone.

FIG. 5 is an electrical circuit diagram of an electric pulser means for supplying pulses to the, lithotrite illustrated in FIGS. 2 and 3. The electric pulser meansof FIG. 5 includes a suppression filter St) to filter out radio frequency or other undesirable electrical transients. The input alternanng voltage from the power mains is connected directly to the suppression filter 5d. The A. C. power is fed from the suppression filter 50 to the electric pulser with one line passing through an on-off power switch 52..

The input power also passes through an input voltage selector switch 54 which includes a pair of movable contact arms 56:, 58. Movable contact arm 56 is con nected at one end to a stationary contact 60. The other end of the contact arm 56 can be switched between stationary contacts 62 and 64-. Similarly, the movable contact arm 5? has one end connected to a stationary contact 66 and the other end is switchable between stationary contacts tit? and 76b. The two movable contact arms 56, 58 are mechanically linked together so as to be simultaneously switched from one position to the other.

The movable contact arm 58 is used to select the appropriate operating voltage for a first transformer 72 which has a primary winding having two sections 74, 76. If the input power is 220 volts A.C., the movable arm 5% is moved into connection with fixed contact 68 which is connected to the upper section 76 of the primary of transformer 72. In this way, if the input A.C. is 220 volts, the entire primary of transformer 72 is used. On the other hand, if the input power is 1 volts A.C., then the movable contact 58 is switched to fixed contact 70 which is connected to the lower portion 74 of the primary of transformer 72. In this way, only the lower portion 74 of the transformer primary is used when the input voltage is 1 10 volts.

Transformer 72 supplies the necessary alternating and direct current for various miscellaneous elements of the electric pulser. Transformer 72 has a first secondary winding 78. Secondary winding 78 has a number of taps which are connected to a lamp voltage control switch 80. The lamp voltage control switch 80 has a movable member 82 to select the appropriate operating voltage for the cystoscope lamp 84. In addition to selecting the appropriate voltage for the cystoscope lamp 84, there is also provided a variable resistor 86 to adjust the brightness of the cystoscope lamp. Finally, a resistor 88 is connected from one tap of the secondary winding 78 directly to the cystoscope lamp 84 so as to assure that there will be some power supplied to the cystoscope lamp at all times in case of a failure in the lamp voltage control switch 80 or the brightness control 86.

Transformer 72 has an additional secondary winding 90 which is used to provide power for additional functions of the electric pulser. One end of secondary winding 90 is connected to a clamp 92 which is used for grounding the system, as will be explained in detail hereinafter. The other end of secondary winding 90 is fed through a diode 94 and filter capacitor 96 so as to form a D. C. power supply for a control relay 98. Therefore, the diode 94 is connected to the operating coil 99 of relay 98. The other side of coil 99 is connected to a plug 100. Plug 100 may be mounted at a suitable location on the cabinet which encloses the electric pulser.

A manually operable device, such as a foot switch 102, is provided for activation of the electric pulser. One side of the foot switch 102 is connected to the plug 100 and the other side is connected to a second plug 104 which is also mounted in the cabinet housing the electric pulser. The plug 104 is connected to the chassis or cabinet of the electric pulser, as indicated by the solid square symbol (indicating chassis, as opposed to earth, ground).

Since this instrument is intended for use on living patients, attention to the problem of protecting against electric shock hazards is necessitated. For this reason, safety considerations require that the cabinet and other portions of the electric pulser be securely connected to earth or some type of external electric ground. This may be accomplished by way of clamp 92. The clamp 92 has two prongs 106, 108 which are shown in firm electrical and mechanical contact with an external electric ground such as, for example, a water pipe 110. It will be noted that the prongs 106, 108 of clamp 92 are electrically insulated from one another since prong 106 is electrically and mechanically connected to the metallic body of the clamp 92, whereas the prong 108 is mounted in a block of insulation material 112 which forms a portion of clamp 92.

The importance of the construction of clamp 92 will be apparent when the circuit for activating the pulser is examined in detail. Note that one end of the secondary winding 90 of transformer 72 is fed by way of tenninal 1114 to the insulated prong 108 of the clamp 92. The other end of secondary winding is fed via diode 94 through the coil 99 of control relay 98 to the foot switch 102. Since the foot switch 102 returns to the cabinet or chassis ground via plug 104, it will be apparent that the foot switch 102 cannot energize control relay 98 unless the other side of the transformer secondary 90 (that is, the side connected to terminal 114) is somehow also connected to the chassis ground so as to complete the circuit. As can be seen by examination of FIG. 5, this is only accomplished when the clamp 92 is securely affixed to an external electric ground. In this way, the clamp 92 acts as a protective means to prevent energization of the electric pulser except when the pulser is securely connected to an external electric ground.

In addition to providing the clamp 92 for rendering the pulser inoperative unless it is externally electrically grounded, there is also provided a ground detector lamp 116 which is connected from the lower end of transformer secondary 90 to the chassis ground. For the same reasons as those set forth above, it will be apparent that the lamp 116 will not be illuminated unless the clamp 92 is securely fastened to an external electric ground.

In addition to the ground detector lamp 116, there is also provided a power supply monitoring lamp 118 which is connected between one winding of transformer secondary 78 and the chassis ground. Lamp 1 18 will therefore continuously indicate whether the electrical circuitry for supplying power to the cystoscope lamp 84 is operative.

Assuming that the clamp 92 is firmly fixed to an external electric ground, the operation of the electric pulser following operation of the foot switch 102 will now be explained. Depressing foot switch 102 energizes the coil 99 of relay 98. This causes a movable contact 120 of relay 98 to be attracted to a fixed contact 122 so as to close the circuit therebetween. The fixed contact 122 is connected to one of the input power lines coming from the suppression filter 50. The movable contact 120 is connected to the fixed terminal 60 of the voltage selector switch 54. The movable contact 56 of the voltage selector 54 is placed in the proper position so as to be correlated with the input voltage. This contact is used to relay power from the contacts of relay 98 to the pulse frequency selecting transformer 124.

Transformer 124 has a number of taps on its primary winding 126. The upper half of primary winding 126 has a number of taps which will be used if the voltage selector switch 54 is in the 220 volt position, whereas the taps on the lower portion of the primary winding 126 are used if the input voltage is 110 volts. A pulse frequency selector switch 125, having two ganged movable contact members 127, 129, is provided to select the desired taps on transformer primary winding 126.

Transformer 124 has a first secondary winding 128 which is connected to a lamp 130. When the primary of transformer 124 is energized, lamp 130 will be illuminated and therefore can be monitored to assure that this portion of the electric pulser is operating properly.

Transformer 124 has a second secondary winding 132 which is connected at one end to a plurality of positively poled rectifiers 134, 136, 138 and 140. Each of these positively poled rectifiers has a bypass resistor so as to assure continuing operation of the system if one of these rectifiers should fail. This same end of the transformer secondary 1132 is also connected to a plurality of negatively poled rectifiers 142, 1144, T46 and 148, which are similarly equipped with bypass resistors.

The positively poled series diodes feed through a resistor 150 to a capacitor 152, whereas the negatively poled diodes feed through a resistor T54 to a capacitor 156. The junction point of capacitors H52 and 156 is connected back to the other end of the transformer secondary 132 so as to form a conventional rectifier with a voltage doubling circuit of a well-known type.

The output of the voltage doubler is fed to a plurality of spark gaps 158, 160 and 162, each of which includes a pair of spark discharge members. Spark gaps 1158, 162 are connected in parallel to one side of the voltage doubler, whereas the spark gap 160 is connected to the other side of the voltage doubler. in the described embodiment, this provides a selection between a so-called so and hard mode of operation. in the soft mode of operation, the lithotrite is connected between spark gaps 158 and 160. The distance between the discharge members forming these two spark gaps may be approximately equal and relatively small so that the amount of voltage required to ionize these two gaps (and thereby generate a pulse for the lithotrite) is relatively small. For this reason, the amount of energy in each pulse can be referred to as being comparatively low, and for this reason, also, this is referred to as the soft mode.

On the other hand, connection of the lithotrite in series between spark gaps 1160 and 162 is referred to as the hard mode because the distance between the discharge members of spark gap 162 is comparatively large with respect to the distance between the discharge members of spark gap 158. For this reason, the amount of voltage which will be accumulated by the voltage doubler before the spark gap 162 ionizes is larger, and thus the amount of energy transferred to the lithotrite when this gap ionizes is greater than that which was transferred to it in the so-called soft mode.

Representative figures for specific types of spark gaps (such as, for example, the spark gaps illustrated and described in detail with respect to H6. 6) reveal that the distance between the discharge members of spark gaps 158 and 160 should be about 0.3 millimeters, whereas the distance between the discharge members of the spark gap 162 may be as much as 0.7 millimeters. In addition, the separation between the inner and outer electrodes of the lithotrite 10 may be approximately 0.5 millimeters.

The lithotrite 10 may be directly connected to a pair of spark gaps or, alternatively, may be connected to the spark gaps by way of a pulse shaping means M4. The pulse shaping means 164 includes a pair of resistors 166, 168 connected to form a conventional voltage divider. The pulse shaping means 164 also contains a pulse shaping circuit consisting of diode i170, resistor 172, and capacitor 174. The lithotrite 110 is then connected across the diode 170.

From the foregoing, it will be apparent that the electric pulser of FIG. 5 can be adjusted in two different ways so as to vary the characteristic of the hydraulic shock wave emitted by the lithotrite lltl. By adjusting the position of the pulse frequency selector switch 125, the frequency of the generated electrical pulses can be increased. This is done by advancing the movable contacts 1127, 112% from the lower to the higher numbered taps, thereby increasing the voltage out of secondary winding 1132. if the pulse frequency is increased without varying the characteristics of the spark gaps, the hydraulic shock Waves generated by the lithotrite 10 will increase in frequency and provide a greater destructive force.

In addition to increasing or decreasing the frequency of the hydraulic shock waves, it is also possible to adjust the elecuic pulser of MG. 5 so as to vary the intensity of the hydraulic shock waves. As pointed out hereinbefore, this is done by varying the characteristics of the spark gaps, as, for example, increasing the distance between the spark discharge members.

With these variations, the physician operating the instrument comprising the present invention has the ability to work with the lowest force which is effective to crush the concretions and thereby minimize the likelihood of damage to any membranes. llfthe applied force is not sur'ficient, small adjustments are possible to gradually increase the force. At its highest setting, the instrument is capable of crushing very hard concretions.

in one particular embodiment of the electrical circuit of FIG. 5, the components shown therein had the following representative values:

Resistor 86 25 ohms Resistor S3 50 ohms Resistors 156, 1154 2K ohms Resistor 16% 4.7 ohms Resistor 1168 0.3 ohms Resistor 172 20K ohms Capacitor 96 Capacitors 1152, 156 Capacitor 1174 Gap spacing, spark gaps 15B, 164) Gap spacing, spark gap 1162 200 microfarads 0.25 microfarads 0.25 microfarads 0.3 millimeters 0.7 millimeters Turning now to FIG. 6, there is shown the details of the spark discharge member assembly which forms part of the electrical pulser of FIG. 5. The spark discharge device of FIG. 6 includes a pair of essentially cylindrical metal members 1180 which have their plane-parallel butt ends facing one another so as to form a discharge gap therebetween. The cylindrical metallic members Th0 may be constructed of any conductive material which will withstand arcing with minimum adverse effeet on the surfaces between which the arcs occur. It has been found that tungsten has particularly desirable characteristics in this device.

The cylindrical metallic members ldll; are fitted into externally threaded collets 182. An insulating case 184 is provided with a pair of fixed annular members 183 having internal threads which encase the threads on collets 182. At the opposite end of each of the collets Th2 and rigidly secured to the corresponding cylindrical metallic members me there is provided an opening 186 which is suited for receiving a tool such as a screwdriver, so as to provide for ready control of the spacing between the facing ends of the two metal cylinders and so as to form the desired size air gap. This particular construction is especially desirable since it also allows the metallic cylinders to be removed from the insulating housing so that the spark gap surfaces may be burnished or otherwise treated to remove any pits that may form therein.

The openings W6 in collets M32 may also serve as connectors to terminals for the high voltage cables that pass from the spark discharge members to the lithotrite and for the internal wiring leading to the spark gap.

Finally, there is provided an opening 188 in the insulated outer case 184 through which the spark gap can be checked and calibrated after the entire spark discharge device is assembled. A spark gap tool having the desired thickness, e .g., 3 mm. or 7 mm., can be inserted through opening 188 to thereby provide a precise measurement of the spark gap spacing.

Turning now to FIG. 7, a further important feature of the invention resides in the connecting cable which connects the electrical pulser means to the novel electrode, which is illustrated and has been described in connection with FIGS. 2, 3, 5, and also 7. With reference to FIG. 7, the preferred cable is divided into two portions, 200 and 202. Cable 200 has at one end two jacks 204 and 206, each comprising a central conductor 205 and 207, and an outer metallic housing as is conventional with a shielded cable. A junction element 208 is conveniently located so that the two separate shielded cables 210 and 212 can be consolidated into one cable 214 which consists of two inner conductors, each with its own insulation, continuing from conductors 205 and 207, respectively. One outer grounded shield (not shown) is provided under a sheath of insulation in cable 214.

At plug 216, the shielding of the cable 200 is terminated, and no part of cable 202, including the electrode region at 10, is shielded or connected to ground.

Plug 218, which is at one end of the lithotrite cable 202, connects with plug 216. A suitable key is provided to mate with keyway 220 in plug 216 to thereby assure the proper polarity as different lithotrites are connected to plug 216. The flexible cable 202 extending from plug 218 should be only as long as essential in order for the electrode to be passed through the cystoscope in the urinary tract ofthe patient and into the bladder region where the concretions are to be crushed. A length of cable 202 of about one-half meter has been found satisfactory.

Because of the flexibility requirements imposed on cable 202, and also considering the inside diameter of the cystoscope, severe restrictions are imposed on the outer diameter of cable 202. At the same time, the two conductors 222 and 224 which carry the electric pulses of high voltage necessary for creating the hydraulic shock wave must be adequately insulated from each other and from outside connections with the hands of the doctor and, of course, the cystoscope extending into the body of the patient.

It has been found that the preferred construction for the cable 202 is to have insulation 226 around the central conductor 222 which is preferably of material other than copper, such as steel. Conductor 224 may be an uninsulated copper wire of about the same diameter as conductor 222 and extend alongthe outside of the insulation 226 on conductor 222.. As illustrated in dashed lines in FIG. 7, conductor 224 may follow a helical path. At electrode 10, conductor 224 is secured to the outer cylinder 9 as by welding.

Insulation 226 needs to have an outer diameter of about 2 to 2.5 mm. to provide adequate insulation, and cannot be materially greater because of the limitations imposed on the maximum diameter of flexible cable 202, as discussed above. However, at the electrode region 10, the spacing between the central conductor 9 and the inside of the cylindrical electrode 10 reduces to about 0.35 mm. through a gradual taper adjacent the electrode region 10. The insulation material between central conductor 9 and cylinder 7 may be a. suitable mastic. The cylinder 8 which serves as the outer electrode has a length between about 1 and 1.35 cm., and an outer diameter of about 2.5 mm.

The outer tubing 226 of insulation material forming part of flexible cable 202 is a continuous sheath which extends from plug 218 to cover all or at least the part of the outer electrode 8 containing the connection between wire 224 and electrode 8. The diameter of tubing 226 of insulation material should be substantially uniform and sufficiently small to pass freely through the cystoscope. A diameter of about 6 mm. has been found to satisfactorily meet all the requirements, including the provision of sufiicient insulation over wire 224 to eliminate any sensation of electricity during the operation of the pulser 230 in FIG. 7.

Three coaxial cable terminals 232, 234, and 236 are provided, which are associated with spark gaps 158, 160, and 162 of FIG. 5. Conductor 207 may be made with a larger diameter than conductor 205 so that conductor 207 fits only in terminal 234, which is associated with spark gap 160, whereas conductor 205 will fit in either terminal 232 or 236. I

Cable 200, being a shielded coaxial cable, can be of whatever reasonable length that may be needed since it has reasonably good electrical pulse transmission properties, which means there is no undue attentuation or distortion of the electrical signals. The shielding terminates at plug 216. Flexible cable 202, however, cannot have an outer shield of conductive material be cause of the limitations imposed by the necessity for it to fit within the cystoscope.

The method of using the instruments described in detail above will now be explained. Prior to the actual crushing of urinary concretions, it is necessary to properly prepare the patient. In order to mitigate pain and prevent spasms of the urinary tract, the patient will initially receive a subcutaneous injection, preferably pipolphen or promedol with atropine, 30 to 40 minutes before the operation. Approximately 10 to 15 minutes before the operation, the urethra is anesthetized with either lidocaine or novocaine. lfthere are spasms of the bladder after the operation commences, the operation should be interrupted and the bladder washed out several times with small volumes of novocaine. This will usually enable resumption and completion of the operation. In certain exceptional situations, it may be necessary to carry out the operation under general anesthesia, particularly in situations where the patient does not properly respond to local anesthesia.

After having completely prepared the patient, a cystoscope (surgical, multi-purpose or model Mackarty urethrocystoscope is introduced into the patients urinary tract. Selection of the cystoscope can be particularly important in assuring the success of this operation. Preference should be given to the type of cystoscope which has a reverse curvature of the tube and a lower position of the window. In addition, the cystoscope operational channel should be sufficiently large in diameter to allow the passage of fragments after having completed the crushing operation.

After having introduced the cystoscope, the bladder should be filled with a dielectric fluid, preferably boiled water and an antiseptic such as rivanol until the patent has urge to urinate. After having filled the bladder with the irrigation fluid, the optical portion of the cystoscope will then be inserted into the operational chanllll nel. As was explained above with respect to H6. 5, this instrument includes the necessary power supply for the cystoscope lamp 84. After having determined the appropriate lamp voltage, this voltage is selected on the lamp voltage control switch 80 of FIG. and the intensity of the cystoscope lamp can then be adjusted by way of resistor 86. At this point, the general condition of the bladder, mucus, membrane, prostate gland, and diverticulum should be examined as well as ascertaining the position, shape and color of the concretion to be crushed.

After having thoroughly examined the bladder and noted the characteristics of the concretion to be crushed, the lithotrite is inserted through the operational channel of the cystoscope. The working end of the lithotrite is then positioned with the aid of m instrument such as an Albarran lingula, until it is pointing to ward and in close proximity to the concretion to be crushed. At this point, it is important to assure that the working end of the lithotrite is positioned normal to the surface of the concretion, and it may be placed in contact against the concretion.

Before beginning a crushing operation, it may be preferable to familiarize the patient with the feel of the lithotripsy operation by giving one or two short blasts of hydraulic shock waves (0.1 to 0.2 seconds). After having ascertained that the efiect of lithotripsy is not unduly painful to the patient, the actual crushing operation can commence.

Initially, the instrument will be set in the soft mode described in detail above with reference to FIG. 5. Until the physician operating this instrument becomes thoroughly familiar with its capabilities, he will usually begin by setting the pulse frequency selector switch 125 at the number 1 position so as to begin by generating hydraulic shocks of the minimum frequency and intensity. Tests with this instrument have been successful in crushing a variety of concretions including those of phosphate salts and carbonates, oxylates, and urates with polished surfaces. After gaining experience with this instrument, it may be possible, taking into account the characteristics of the concretion, to begin at other than minimum frequency and intensity.

The actual crushing operation is then instituted by depressing the foot switch 102 for a brief period of time (not longer than 1 second). During this interval, a large number of impulses is generated. if the concretion is not fractured (i.e., either cracked or completely broken) by the initial hydraulic burst, it is necessary to wait at least seconds before a further attempt is made.

After having made from three to five unsuccessful attempts at the lowest setting of the instrument, the pulse frequency selector switch 125 may be then advanced to a number 2 position, or higher, and the sequence set forth above is repeated at this setting. Operation continues in this fashion until the number 5 position is reached. If the concretion is still not crushed at this point, it is possible to go into the hard mode described above with respect to FIG. 5. This can be accomplished, for example, by removing the actual high voltage cable 165 which feeds to the lithotrite l0 and inserting it into a different set of plugs. Alternatively, this selection could be accomplished by simple switching arrangements provided with the instrument.

After having changed to the hard mode, the pulse frequency selector switch 125 should be returned to a lower setting before lithotripsy is commenced. As was explained above with respect to operation in the soft mode, attempts to crush the concretion are carried on with increases in the setting of the pulse frequency selector switch 112$ until such time as the concretion is at least cracked, if not completely crushed. At this point, it is desirable to reduce both the power and duration of the hydraulic shocks to a minimum, and to reposition the end of the lithotrite near the surface of the newly formed cavity in the concretion for further applications of impulses.

The technique described above is carried out until such time as the concretion is crushed into fragments which are small enough to pass through the operational channel of the cystoscope.

After having crushed the concretions into fragments which can be removed through the operational channel of the cystoscope, it is then necessary to remove the crushed fragments in some way. The first step is to remove the liquid solution which was injected into the bladder at the beginning. When this liquid is removed, a number of the stone fragments will naturally be withdrawn at that time.

After having removed the dielectric liquid, and having withdrawn the lithotrite from the operational channel of the cystoscope, a lanets syringe or Bigelows aspirator can then be connected with the cystoscope tube. An irrigation liquid can then be injected into the bladder, preferably in small, intermittent portions so as to create an eddy. The syringe is then disconnected, and the stone fragments are washed out by the back flow. If the stones are small, it may be possible to wash out all the fragments after a single irrigation. Finally, there may be some very fine particles which will lodge in certain portions of the bladder but these fine particles can be disregarded since they will generally be passed out in a few days following the operation with the normal emission of the urine.

If the concretions are unusually hard, or large in number, it may not be possible to completely crush all of them in one single operation. in this case, the cystoscope can be removed and a catheter introduced into the urinary tract and left there until the next treatment, preferably within two or three days following the first treatment.

While preferred embodiments of the present invention have been illustrated and described, it is, of course, understood that various modifications and changes may be made therein without departing from the true spirit and scope of the invention as defined in the appended claims when accorded a full range of equivalents.

What is claimed is:

l. An instrument for crushing concretions in a urinary tract comprising: an electric pulser means having a pair of output terminals and a power transformer having a high voltage secondary winding, electrical circuitry connected between said high voltage secondary winding and said terminals including capacitor means, spark discharge members forming at least one electrical discharge gap of a predetermined size for breaking down when said capacitor discharges and being connected in series circuit relationship with said terminals and across said capacitor means, and a lithotrite having two electrodes electrically connected to said output terminals and insulated from each other and adapted for being positioned into the urinary tract adjacent a concretion to be crushed, one of said electrodes being a central conductor and the other electrode being an outer substantially cylindrical conductor coaxially surrounding said central conductor; and a manually operable device for remote control of said pulser means to thereby produce an electrical discharge between said lithotrite electrodes when discharging said capacitor means across said gap.

2. The instrument recited in claim 1 together with lithotrite positioning means comprising a cystoscope having a hollow operational channel through which said lithotrite electrodes are adapted to pass, and means for illuminating the portion of the lithotrite adjacent the concretionto be crushed.

3. The instrument recited in claim 1 further comprising electrical protective means operatively connected between said manually operable device and said pulser means, and protective means comprising a circuit member adapted for connection between an external electric ground conductor and a portion of the circuit in the electric pulser means whereby failure to have such connection prevents operation of said instrument.

4. The instrument recited in claim 1 wherein said coaxial electrodes have butt end portions located in substantially a single plane with an insulative covering on said inner electrode extending'up to said butt end portions.

5. The instrument recited in claim 1 wherein said coaxialelectrodes have butt end portions located in different planeswith said inner electrode and an insulative covering thereon both extending beyond the butt end portion of said outer electrode.

6. The instrument recited in claim 1 wherein said spark discharge members comprise a pair of metallic cylinders having plane-parallel opposed discharge butt end surfaces to form said discharge gap.

7. The instrument recited in claim 6 wherein said cylinders are formed of tungsten. 8.'The instrument recited in claim 1 wherein said electrical circuitry includes two pairs of spark discharge members, the members of each pair being separated so as to form an electrical discharge gap and being connected in series circuit relationship between said coaxial electrodes and said capacitor means.

,9. The instrument recited in claim 8 wherein said spark discharge members have spacings between about 0.3 and 0.7 millimeters, and the spacing between the coaxial electrodes is approximately 0.5 millimeters.

10. The instrument recited in claim 1 wherein said electrical circuitry includes three pairs of spark discharge members, the members of two of said pairs being separated with substantially equal spacings, and the members of the third pair being separated with a different spacing; and means for controlling the intensity of the discharge between said coaxial electrodes including means for optionally connecting either said two pairs in operative relation with said coaxial electrodes or said third pair and only one of said pairs in operative relation with said coaxial electrodes.

11. An instrument for crushing stones in the urinary bladder comprising in combination: an operativecystoscope having a hollow interior and an illuminating lamp; an elongated lithotrite adapted for introduction through the interior of said cystoscope and having an inner and an outer electrode insulated from each other and adapted to extend beyond one end of the cystoscope, and conductor members adapted to extend through the cystoscope interior and beyond the other cystoscope end; electric pulser means connected to said lithotrite conductor members and comprising a power transformer having windings located on separate legs and air gaps between the windings and the legs; an electrical grounding system connected with said cystoscope lamp; a device for remote control of said transformer connected to it through said grounding system; an accumulating device with capacitors fed from said power transformer and at least one pair of tungsten cylinders connected between said electrodes, the tungsten cylinders having plane-parallel opposed discharge butt end surfaces, and means for changing the discharge gap spacing between said end surfaces.

12. An instrument for crushing stones in the urinary bladder as claimed in claim 11, wherein the lithotrite electrodes have end portions which are positioned in different planes while the insulation between the electrodes covers the inner electrode up to its end and extends beyond the end of the outer electrode.

13. An instrument for crushing stones in the urinary bladder comprising in combination: an operative cystoscope having a hollow interior; an elongated lithotrite adapted for introduction into a urinary bladder through the interior of said cystoscope and having two coaxial electrodes insulated from each other with each of said electrodes having butt end portions separated by a gap adapted to extend beyond one end of the cystoscope; and electric pulser means connected to said lithotrite for causing an electric breakdown of the gap formed between the butt end portions of said electrodes when the electrodes are immersed in a liquid medium as a result of which a hydraulic shock wave is formed in the liquid medium, said electric pulser means including a pair of spaced discharge members connected in series circuit relationship with said electrode gap.

14. An instrument for crushing stones in the urinary bladder comprising in combination: an operative cystoscope having a hollow interior and an illuminating lamp; an elongated lithotrite adapted for introduction into a urinary bladder through the hollow interior of said cystoscope and having two coaxial electrodes insulated from each other; grounding means for said lithotrite connected with said cystoscope lamp; and electric pulser means connected to said electrodes comprising a power transformer, a device for remote control of said transformer connected with the transformer, an accumulating device including capacitors fed from said power transformer, and pulse-forming dischargers including a pair of spaced discharge members connected with the electrodes of said lithotrite and with said accumulating device.

15. An instrument for crushing concretions in a urinary tract comprising:

two coaxial electrodes insulated from each other, one

of said electrodes being a central conductor and the other being an outer conductor surrounding said central conductor, said electrodes having butt end portions located in substantially a single plane with insulation covering the central electrode up to the butt end portion;

means for positioning said electrodes in a urinary bladder adjacent a stone to be crushed; and electric pulser means connected to said coaxial electrodes and including a power transformer having a high voltage winding, a manually operated device for remote control of said electric pulser means,

and an accumulating device including capacitors connected to be energized from said power transformer and two pairs of spark discharge members forming two discharge gaps connected in series with the gap between said electrodes and across the accumulating device, said two discharge gaps being between a pair of plane-parallel, opposed butt end surfaces of said discharge members.

16. A method of crushing concretions in the urinary tract comprising the steps of:

a. providing a cystoscope having an operational channel, an optical portion and an illuminating p;

b. inserting said cystoscope into the urinary tract;

c. filling the urinary bladder with a washing fluid;

d. examining the bladder with the optical portion of the cystoscope so as to locate and examine the concretion tobe crushed;

e. inserting an electro-hydraulic lithotritehaving a working end into the operational channel of the cystoscope;

f. positioning the working end of said electrohydraulic lithotrite adjacent the concretion to be crushed; and

g. manually operating a remote control device so as to activate an electric pulser connected to the electro-hydraulic lithotrite and generate hydraulic shock waves to crush the concretion.

17. The method recited in claim 16 wherein step (g) comprises the steps of:

a. setting the electric pulser so as to be conditioned to generate hydraulic shock waves of a first intensity and repetition frequency;

b. manually operating said remote control device so as to activate said electric pulser and generate said hydraulic shock waves of said first intensity and repetition frequency;

c. optically examining said concretion to determine whether the concretion has fractured; and

d. in the event that the concretion has not fractured, adjusting the setting of the electric pulser so as to change the intensity and repetition frequency of said hydraulic shock waves, and repeating the above steps (e), (f), and (g).

18. For use with an instrument for crushing stones in the urinary bladder, a cable member having at one end a connector terminal member having a pair of insulated conductors for connection to a mating terminal member supplied with power from said instrument and at the other end two electrodes, one of said electrodes being a central conductor and the other electrode being an outer, substantially cylindrical electrode coaxially disposed relative to said central conductor and separated from said central conductor by insulation material having a thickness of at least about 0.35 millimeters; a flexible cable having a length sufficient to extend through the urinary tract and into the urinary bladder comprising a central insulated wire, a second wire connecting said electrodes to said connector terminal member, and a tubing of insulation material extending as a unitary member of substantially uniform diameter between the connector terminal member and said electrode and covering the outer surface of said outer electrode, said tubing having a thickness sufficient to prevent arcing to other conducting materials and an outside diameter sufficiently small to allow insertion of said electrodes through the urinary tract into the urinary bladder.

19. Apparatus as defined in claim 18 wherein the second wire is an uninsulated single wire of sufficiently small diameter to extend along the other surface of the insulation on the central wire and under the inner surface of said tubing of insulation material to thereby and not materially decrease the flexibility of said flexible cable.

20. Apparatus as defined in claim 19 wherein said flexible cable has a length of approximately one-half meter and an outside diameter of approximately six millimeters, the central insulated wire is not copper, and said second wire is copper.

21. Apparatus as defined in claim 18 together with a second cable having at one end a connector terminal member adapted to mate with the connector terminal member of said lithotrite and at the other end a pair of coaxial terminals, each having an insulated inner conductor and an outer coaxial shield, a junction member for merging said two insulated conductors inside a single outer coaxial shield which extends from said junction member to the vicinity of, but not beyond, said connector terminal member on said second cable.

:ik :1: :1 i3: :3 

1. An instrument for crushing concretions in a urinary tract comprising: an electric pulser means having a pair of output terminals and a power transformer having a high voltage secondary winding, electrical circuitry connected between said high voltage secondary winding and said terminals including capacitor means, spark discharge members forming at least one electrical discharge gap of a predetermined size for breaking down when said capacitor discharges and being connected in series circuit relationship with said terminals and across said capacitor means, and a lithotrite having two electrodes electrically connected to said output terminals and insulated from each other and adapted for being positioned into the urinary tract adjacent a concretion to be crushed, one of said electrodes being a central conductor and the other electrode being an outer substantially cylindrical conductor coaxially surrounding said central conductor; and a manually operable device for remote control of said pulser means to thereby produce an electrical discharge between said lithotrite electrodes when discharging said capacitor means across said gap.
 2. The instrument recited in claim 1 together with lithotrite positioning means comprising a cystoscope having a hollow operational channel through which said lithotrite electrodes are adapted to pass, and means for illuminating the portion of the lithotrite adjacent the concretion to be crushed.
 3. The instrument recited in claim 1 further comprising electrical protective means operatively connected between said manually operable device and said pulser means, and protective means comprising a circuit member adapted for connection between an external electric ground conductor and a portion of the circuit in the electRic pulser means whereby failure to have such connection prevents operation of said instrument.
 4. The instrument recited in claim 1 wherein said coaxial electrodes have butt end portions located in substantially a single plane with an insulative covering on said inner electrode extending up to said butt end portions.
 5. The instrument recited in claim 1 wherein said coaxial electrodes have butt end portions located in different planes with said inner electrode and an insulative covering thereon both extending beyond the butt end portion of said outer electrode.
 6. The instrument recited in claim 1 wherein said spark discharge members comprise a pair of metallic cylinders having plane-parallel opposed discharge butt end surfaces to form said discharge gap.
 7. The instrument recited in claim 6 wherein said cylinders are formed of tungsten.
 8. The instrument recited in claim 1 wherein said electrical circuitry includes two pairs of spark discharge members, the members of each pair being separated so as to form an electrical discharge gap and being connected in series circuit relationship between said coaxial electrodes and said capacitor means.
 9. The instrument recited in claim 8 wherein said spark discharge members have spacings between about 0.3 and 0.7 millimeters, and the spacing between the coaxial electrodes is approximately 0.5 millimeters.
 10. The instrument recited in claim 1 wherein said electrical circuitry includes three pairs of spark discharge members, the members of two of said pairs being separated with substantially equal spacings, and the members of the third pair being separated with a different spacing; and means for controlling the intensity of the discharge between said coaxial electrodes including means for optionally connecting either said two pairs in operative relation with said coaxial electrodes or said third pair and only one of said pairs in operative relation with said coaxial electrodes.
 11. An instrument for crushing stones in the urinary bladder comprising in combination: an operative cystoscope having a hollow interior and an illuminating lamp; an elongated lithotrite adapted for introduction through the interior of said cystoscope and having an inner and an outer electrode insulated from each other and adapted to extend beyond one end of the cystoscope, and conductor members adapted to extend through the cystoscope interior and beyond the other cystoscope end; electric pulser means connected to said lithotrite conductor members and comprising a power transformer having windings located on separate legs and air gaps between the windings and the legs; an electrical grounding system connected with said cystoscope lamp; a device for remote control of said transformer connected to it through said grounding system; an accumulating device with capacitors fed from said power transformer and at least one pair of tungsten cylinders connected between said electrodes, the tungsten cylinders having plane-parallel opposed discharge butt end surfaces, and means for changing the discharge gap spacing between said end surfaces.
 12. An instrument for crushing stones in the urinary bladder as claimed in claim 11, wherein the lithotrite electrodes have end portions which are positioned in different planes while the insulation between the electrodes covers the inner electrode up to its end and extends beyond the end of the outer electrode.
 13. An instrument for crushing stones in the urinary bladder comprising in combination: an operative cystoscope having a hollow interior; an elongated lithotrite adapted for introduction into a urinary bladder through the interior of said cystoscope and having two coaxial electrodes insulated from each other with each of said electrodes having butt end portions separated by a gap adapted to extend beyond one end of the cystoscope; and electric pulser means connected to said lithotrite for causing an electric breakdown of the gap formed between the butt end portions of said electRodes when the electrodes are immersed in a liquid medium as a result of which a hydraulic shock wave is formed in the liquid medium, said electric pulser means including a pair of spaced discharge members connected in series circuit relationship with said electrode gap.
 14. An instrument for crushing stones in the urinary bladder comprising in combination: an operative cystoscope having a hollow interior and an illuminating lamp; an elongated lithotrite adapted for introduction into a urinary bladder through the hollow interior of said cystoscope and having two coaxial electrodes insulated from each other; grounding means for said lithotrite connected with said cystoscope lamp; and electric pulser means connected to said electrodes comprising a power transformer, a device for remote control of said transformer connected with the transformer, an accumulating device including capacitors fed from said power transformer, and pulse-forming dischargers including a pair of spaced discharge members connected with the electrodes of said lithotrite and with said accumulating device.
 15. An instrument for crushing concretions in a urinary tract comprising: two coaxial electrodes insulated from each other, one of said electrodes being a central conductor and the other being an outer conductor surrounding said central conductor, said electrodes having butt end portions located in substantially a single plane with insulation covering the central electrode up to the butt end portion; means for positioning said electrodes in a urinary bladder adjacent a stone to be crushed; and electric pulser means connected to said coaxial electrodes and including a power transformer having a high voltage winding, a manually operated device for remote control of said electric pulser means, and an accumulating device including capacitors connected to be energized from said power transformer and two pairs of spark discharge members forming two discharge gaps connected in series with the gap between said electrodes and across the accumulating device, said two discharge gaps being between a pair of plane-parallel, opposed butt end surfaces of said discharge members.
 16. A method of crushing concretions in the urinary tract comprising the steps of: a. providing a cystoscope having an operational channel, an optical portion and an illuminating lamp; b. inserting said cystoscope into the urinary tract; c. filling the urinary bladder with a washing fluid; d. examining the bladder with the optical portion of the cystoscope so as to locate and examine the concretion to be crushed; e. inserting an electro-hydraulic lithotrite having a working end into the operational channel of the cystoscope; f. positioning the working end of said electro-hydraulic lithotrite adjacent the concretion to be crushed; and g. manually operating a remote control device so as to activate an electric pulser connected to the electro-hydraulic lithotrite and generate hydraulic shock waves to crush the concretion.
 17. The method recited in claim 16 wherein step (g) comprises the steps of: a. setting the electric pulser so as to be conditioned to generate hydraulic shock waves of a first intensity and repetition frequency; b. manually operating said remote control device so as to activate said electric pulser and generate said hydraulic shock waves of said first intensity and repetition frequency; c. optically examining said concretion to determine whether the concretion has fractured; and d. in the event that the concretion has not fractured, adjusting the setting of the electric pulser so as to change the intensity and repetition frequency of said hydraulic shock waves, and repeating the above steps (e), (f), and (g).
 18. For use with an instrument for crushing stones in the urinary bladder, a cable member having at one end a connector terminal member having a pair of insulated conductors for connection to a mating terminal member supplied witH power from said instrument and at the other end two electrodes, one of said electrodes being a central conductor and the other electrode being an outer, substantially cylindrical electrode coaxially disposed relative to said central conductor and separated from said central conductor by insulation material having a thickness of at least about 0.35 millimeters; a flexible cable having a length sufficient to extend through the urinary tract and into the urinary bladder comprising a central insulated wire, a second wire connecting said electrodes to said connector terminal member, and a tubing of insulation material extending as a unitary member of substantially uniform diameter between the connector terminal member and said electrode and covering the outer surface of said outer electrode, said tubing having a thickness sufficient to prevent arcing to other conducting materials and an outside diameter sufficiently small to allow insertion of said electrodes through the urinary tract into the urinary bladder.
 19. Apparatus as defined in claim 18 wherein the second wire is an uninsulated single wire of sufficiently small diameter to extend along the outer surface of the insulation on the central wire and under the inner surface of said tubing of insulation material to thereby and not materially decrease the flexibility of said flexible cable.
 20. Apparatus as defined in claim 19 wherein said flexible cable has a length of approximately one-half meter and an outside diameter of approximately six millimeters, the central insulated wire is not copper, and said second wire is copper.
 21. Apparatus as defined in claim 18 together with a second cable having at one end a connector terminal member adapted to mate with the connector terminal member of said lithotrite and at the other end a pair of coaxial terminals, each having an insulated inner conductor and an outer coaxial shield, a junction member for merging said two insulated conductors inside a single outer coaxial shield which extends from said junction member to the vicinity of, but not beyond, said connector terminal member on said second cable. 